Responding to reports that some of his investments have been overseas, Romney insisted his "trustee follows all U.S. laws." He added: "All the taxes are paid, as appropriate. All of them have been reported to the government. There's nothing hidden there."

He accused Obama of trying to distract from his economic record.

"The president is going to try to do anything he can to divert attention from the fact that his jobs record is weak, and he has no plans to make things better," Romney said.

But Romney has so far resisted calls to release additional information about his personal finances, rejecting the approach of his father, George, who released 12 years of returns when he ran for president in 1964.